Electronic computer



Patented Oct. 7, 1947 UNITED STATES seats 'doom PATENT OFFICE ELECTRONIC CORIPUTER of Delaware Application August 29, 1942, Serial No. 456,591

6 Claims.

This invention relates generally to electroni-c computers, and particularly to apparatus for deriving the value of a predetermined function of a selected quantity which is applied to the computer as a voltage proportional in amplitude to the value of the original quantity.

Heretofore, various devices have been disclosed for deriving predetermined functions of quantities applied as driving voltages. Many such systems utilize the scanning action of light beams or cathode rays across especially constructed screens having predetermined ducial markings.

The instant system utilizes the adjustable nonlinearity of resistance of a network which includes a non-linear resistance element such as Thyrite. By a suitable combination of linear resistive elements with such non-linear resistive elements, a voltage applied to the network may provide an output voltage the value of which is a complex function of the input voltage.

For example, it has been found that a Thyrite element combined with a parallel linear resistor and a series linear resistor of predetermined relative values may be made to provide an output voltage directly proportional to the time of flight when a voltage of magnitude proportional t the value of slantl range in a ballistics equation is applied to the network.

The characteristics of Thyrite are described in General Electric Review for April 1934, pages 175-179 and May 1934, pages 218-223 inclusive. The characteristics of particular pieces of Thyrite vary .considerably with size, shape, applied voltage and molecular composition. In general, a particular Thyrite element has a characteristic represented by the formula I=KEU, where K and 'v represent characteristics peculiar to the individual Thyrite element. Since the resistance of a network including a Thyrite element is a function of input voltage, best results are obtained with applied voltages exceeding a predetermined minimum value.

A preferred embodiment of the invention includes a rectifier circuit and a D.C. amplifier which includes inverse-feedback. Such a circuit provides a driving source of negligible impedance for the network described. Output is derived from the network from across the series resistor.

Among the objects of the invention are to provide a new and improved means for deriving a voltage of an amplitude which is a predetermined non-linear function of an applied voltage. Another object is to provide an improved means for deriving a voltage of an amplitude which is a predetermined function of a voltage applied to a network which includes linear and non-linear impedance elements. A further object of the invention is to provide an improved means for deriving an output voltage the value of which is a predetermined function of a voltage applied to a network which includes a Thyrite element and one or more linear resistive elements. Still another purpose of the invention is to provide an improved means for applying voltages to nonlinear networks which include a rectifier and substantially linear D.C. amplifier to provide a driving source of negligible impedance.

The invention will lbe described in greater detail 'by reference to the accompanying drawing of which Fig. 1 is a schematic circuit diagram of a network including linear and non-linear impedance elements, Fig. 2 is a schematic circuit diagram of a preferred embodiment of the invention, and Fig. 3 is a set of explanatory curves relating to the operation of the apparatus of Fig. 2. Similar reference numerals are applied to similar elements throughout the drawing.

Referring to Fig. 1, a voltage El is applied to the terminals I, 2 of a network which includes a Thyrite or other non-linear element 5 which is connected in parallel with linear resistor Rs. One common terminal of the network Rs, 5 is connected to one terminal of a second resistor Rn. The remaining common terminal of the network Rs, 5 is connected to the input terminal I. The remaining terminal of the second resistor Ro is connected to the remaining input'terminal 2 and to one output terminal 4. The remaining output terminal 3 is connected to the common terminal of the network Rs, 5 and the second resistor Re. The output voltage derived from the output terminals 3, 4 is designated as En.

Fig. 3 illustrates how the relation between E0 and El varies with change in the values of Rs and Re. In order to facilitate comparison 0f the different curves, the scale factor of E0 is adjusted so that the curves show the same maximum value of El. It will be noted that the Eo vs. El curve is steep when Ro is small and RS is large. As Rs is lowered or Ro is increased, the average radius of curvature of the curve is increased in different Ways. Thus increasing Rn increases the radius of curvature more at the top of the curve and decreasing Rs increases the radius of curvature more at the bottom of the curve. By using different ratios of Rs/Ro, the curve is made to change shape and still have the same average curvature. It is apparent, of course, that increasing Ro or decreasing Rs increases the output for a given input and so increases the scale factor.

The following table gives the results obtained with a given piece of Thyrite:

In securing this data, Ru was adjusted to 275 ohms and Rs was adjusted to 2000 ohms. The maximum input voltage corresponding to 4300 yards was 28.5 volts giving an input scale factor of about 151 yards per volt. The output for this same input was 8.5 volts giving an output scale factor of about 1.041 seconds per volt. It will be noted that the time of flight values indicated by the Thyrite network approximates very closely those taken from the ta'bles.

Variation of the ratio Rs/Ro, as well as the magnitude of these linear resistive elements, permits a wide variety of network characteristics. It should be understood that the network described is merely typical of one embodiment of the invention and that other networks utilizing Thyrite, or other non-linear impedance elements, may loe used to equal advantage for computing predetermined functions of quantities applied to the network as driving voltages. The values of the function are determined from a function table. RS and Ro are experimentally adjusted by trial and error until the closest approximation to the desired function is obtained. Increasing Rs tends to make the function steeper throughout the curve. Increasing Ro tends to make the function less steep at the high voltage end. The higher the exponent of the cell of Thyrite, the lower Rs will be. Also Ro will need to be increased but not to the same degree that R is decreased. It is apparent that the scale factor of the function will change as Rs and Ro are changed.

Fig. 2 is a modification of the invention which includes means for providing driving voltages. A voltage E, which may, for example be an A.C. potential of amplitude proportional to the particular selected value of the slant range of a ballistic equation, is applied to the input terminals II, I2. The terminal I2 is grounded. Voltages applied to the input terminal II are impressed upon the cathode of a diode rectifier I3 through a coupling capacitor I4. A smoothing reactor 25 is connected between the filter I5 and the cathodes of the duodiode I3. The values of the capacitor I4 and the reactor 25 are not critical. The anode of the diode rectifier I3 is connected to the input of a conventional low pass filter I5, The output of the low pass filter I5 is applied to the control electrode of a rst D.C.' amplifier tube I6 through a source of bias potential, such as a battery I'I. The anode of the first D.C. amplifier I6 is connected to the control electrode of a second D.C. amplifier I 'I which includes an anode voltage regulator device I8 such as an RCA-150 type tube in series with its cathode circuit. The second D.C. amplier I'I includes a degenerative cathode circuit comprising a series capacitor I9 and a series resistor 20 which are connected between the cathode current regulator I8 and ground. The voltage across this regulator functions as a simple bucking voltage to compensate for the positive plate voltage of the tube I'I. Anode voltages are applied to the D.C. amplifier tubes through conventional anode coupling resistors 2|, 22. The second D.C. amplifier II is cathode loaded to derive the voltage Ei from across the degenerative network I9, 20. The voltage Ei is applied to the terminals I, 2 of the network of Fig. 1. The output voltage Eo is derived from the terminals 3, 4 which are connected across the output resistor Ro. 'I'he output voltage En may be indicated directly by a meter 23 connected across the output terminals 3, 4; or the voltages may be applied to other elements of a complete ballistics predictor, not shown. As explained heretofore, the value of En will be a predetermined function of the value of El depending upon the characteristics of the Thyrite element 5, and the relative magnitude of the resistors Rs and R0. Since the rectifier- D.C.-amplifier circuit just described is Substantially linear in operation, the voltage Eo will likewise be a predetermined function of the applied voltage E. The degenerative circuit of the D.C. amplifier provides a coupling circuit of negligible impedance for the input terminals I, 2 of the non-linear network. It is desirable that the impedance of the D.C. amplifier, looking into the network input terminals I, 2, shall tbe constant and lower than the resistor Ro. In general, the input impedance plus the tube impedance should be substantially equal to Ro.

It should be understood that the applied A.C. potential E, having an amplitude proportional to a particular selected value of the slant range in a ballistics equation, may lbe derived in any manner known in the electronic predictor art. The extremely complex methods and apparatus for so deriving the voltage corresponding to the selected slant range form no part of the present invention. The instant device merely derives from the applied voltage a second voltage having a magnitude which is a predetermined function of the applied voltage. The particular function is determined by the known ballistics characteristics of a particular projectile. The function is then set up upon the instant device by adjusting the variable linear resistors Rs and Ro. It further should be understood that the adjustment of the resistors to the particular function may be accomplished by mathematical calculation or by experimental methods. The same procedure may be applied to many other mathematical problems requiring complex solution.

I claim as my invention:

1. Apparatus for computing electronically a predetermined non-linear function of a quantity including a source of voltage of amplitude proportional to the value of said quantity, linear means for deriving af D.C. potential from said source, a network comprising a non-linear impedance element, a rst linear impedance element connected in parallel with said non-linear impedance element, a second linear impedance element connected in series with said parallelconnected elements, and means for applying said D.C. potential across said network, whereby a voltage corresponding to the value of said function of said quantity is produced across said second linear impedance element.

2. Apparatus of the type described in claim l including means for indicating directly the voltage across said second impedance element as a Seam measure of the desired value of said function of said quantity.

3. Apparatus of the type described, in claim 1 characterized lloy the fact that the values of said impedance elements satisfy said function equation when the characteristics of the particular 'I'hyrite element are represented by K and 'D in the equation Where E1 is the voltage applied to the network and Eo is the Voltage across the second impedance element.

4. Apparatus for computing electronically time of night in a lballistics equation when the slant range is known, including a source of voltage of amplitude proportional to the slant range, linear means for deriving a D.C. potential from said source, a network comprising a parallel connected Thyrite element and resistor in which one terminal of each is commonly connected to one terminal of a second resistor, and means for ap- @lying said D.C. potential across said network, whereby a voltage corresponding to the Value of said time of ight is produced across said second resistor.

5. Apparatus of the type described in claim 4 where E: is the voltage applied to the network and En is the Voltage across the second resistor.

ARTHUR W. VANCE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,017,192 Woli Oct. 15, 1935 2,177,050 Bartels Oct. 24, 1939 2,244,369 Martin June 3, 1941 2,251,973 Beale et al. Aug. 12, 1941 2,021,920 Norwine Nov. 26, 1935 2,070,178 Pottenger, Jr., et al. Feb. 9, 1937 2,086,910 Hansel] July 13, 1937 

